I. Technical Field
The present invention relates to a clear paint booth coating composition and method of applying the same to function as a barrier preventing the deposit of paint overspray on equipment and surfaces in a paint spray booth. The coating composition is dissolvable in water or may be peeled off as a film after overspray has accumulated thereon.
II. Brief Description of the Background Art
Paint spray booths are enclosures in which industrial production painting operations are performed. Paint spray booths both protect the paint spraying operation and permit control of emissions from paint spraying operations.
In commercial paint spraying processes, frequently as much as fifty percent of the paint used is not deposited on the object to be painted. Much of the overspray is removed in water wash systems used to scrub the overspray particles from exhaust air. However, some of the overspray is unavoidably deposited on robots, paint spraying equipment, transfer line carriers, paint booth walls and windows. If such objects and surfaces are not protected from the overspray, they can quickly become covered with paint. Paint deposits on robots and paint spray equipment can lead to equipment malfunctions or flaking off of paint on articles being painted which can adversely affect the quality of the painted article. Also, overspray build-up on walls and windows can diminish light levels in the paint spray booth and render windows useless.
The use of hot caustic or methylene chloride strippers to remove overspray suffers serious drawbacks in that the chemicals must be used carefully. Also, if methylene chloride-type strippers are used, the solvents contained in the strippers give off vapors which further burden plant emission control systems. Also, the emissions generated by paint removal operations contribute to the total amount of emissions permitted by environmental regulations and thereby reduce the quantity of emissions that may be generated in production painting operations.
The walls of paint spray booths may be protected by pigmented barrier coatings which are preferably white to make the paint booth brighter. Such pigmented coatings are not appropriate for use on equipment, robots or windows in paint spray booths since such coatings would obscure signs and windows.
Clear coatings are known for application to equipment, robots or windows in paint spray booths but have not been totally satisfactory in all respects. For example, xanthan gum-based clear barrier coatings are not resistant to ketone and aromatic solvents. Since such solvents are common in many paints, overspray particles may partially dissolve the barrier coating and allow some of the overspray to be deposited upon the objects and surfaces in the spray booth coated with the xanthan gum-based coating.
Another known type of clear coatings include urea formaldehyde-based barrier coatings which have better solvent resistance than xanthan gum coatings. However, urea formaldehyde-based coatings tend to have a yellow tint which is objectionable, particularly when applied to windows.
Combination xanthan gum and urea formaldehyde barrier coatings are known and result in a compromise coating which is not as yellow as urea formaldehyde coatings and not as seriously affected by ketone and aromatic solvents as xanthan gum barrier coatings.
Since the barrier coatings must be periodically removed and replaced with a fresh coating, it is vital that the coating be easily removable. Known clear coatings are normally removed in one of two ways, either by water washing or peeling off as a film.
With barrier coatings on equipment and robots, it is preferred to provide a peelable coating which may be removed without application of water that could harm the robots or equipment. On broad, flat surfaces that can be washed off with water or subjected to a high pressure water spray, it is generally preferred to wash the barrier coating off. The barrier coating if washed off must not interfere with the water wash system of the paint spray booth and must be compatible with the filtration or residue removal system used in the paint spray booth. Since known clear barrier coatings are limited to one preferred removal technique, it is generally necessary for optimal performance to use two different types of clear coating in a paint spray booth.
These and other disadvantages are overcome and problems are solved by the present invention's provision of an improved clear paint booth coating composition and method incorporating the use of such a compositions as summarized below.